We have recently initiated a program to develop chimeric antibodies of defined specificity. Such immunoglobin molecules which could be ideal for radiotherapy and radioimaging will include chimeric antibodies with murine variable region and human constant region. Additionally, we plan to generate isotype switch variant of specific monoclonal antibody genes. We will also attempt to manipulate antibody genes that may lead to a change in Fc fragment of the antibody molecule resulting in a desirable change in the biological effector function. Our plans also include generation of pared down antibody molecules (Fab' 2, Fab and FV). Such molecules can be used for antigen clearance without complement activation. Among other desirable variants of antibody molecules that we will attempt to generate by gene manipulation will include, a) antibodies with improved affinity for the target, b) molecules with altered carbohydrate content, and c) antibody molecules that can specifically bind to certain enzymes or toxic substances. To attain our objectives we will initially attempt to clone the cDNA copies of messages for light and heavy chain genes of immunoglobulin synthesized by hybridomas against tumor associated antigens. We will characterize these clones and will attempt expression of the cDNA constructs by inserting them in appropriate vectors and transfecting the construct into myeloma cells. Subsequently, we will attempt to clone the rearranged genomic DNA segments encoding heavy and light chain genes of hybridomas.